Field of the Invention
The present invention relates to a radiation imaging system, a control apparatus, a control method, and a storage medium.
Description of the Related Art
There has been commercialized a radiation imaging system using a radiation generation apparatus which irradiates an object with radiation, a radiation imaging apparatus which generates a clear radiation image by processing the radiation image obtained by digitizing a radiation image as the intensity distribution of radiation, and an image processing apparatus. Such a radiation imaging system transfers, to the image processing apparatus such as a control computer for image processing and storage, radiation image data obtained by the radiation imaging apparatus upon causing the radiation generating apparatus to irradiate an object with radiation. The image processing apparatus displays an image having undergone image processing on a display device such as a display.
The radiation imaging apparatus forms an image based on an electrical signal generated in accordance with radiation. For example, the radiation detection unit of the radiation imaging apparatus includes a sensor array formed by stacking scintillators on photoelectric conversion elements (conversion elements) or the like which convert radiation into image signal electric charges (electrical signals). The radiation imaging apparatus causes the sensor array to convert radiation into visible light through the scintillators, holds the visible light as electric charges, and forms an image from readout electric charges. The radiation imaging apparatus which forms an image from the amount of electric charges requires the elapse of a predetermined time since the energization of a circuit for driving the conversion elements to set an image sensing enable state for image quality stabilization.
For example, Japanese Patent Laid-Open No. 2010-273858 discloses a method of saving power by shortening the time taken to be ready for image sensing. Japanese Patent Laid-Open No. 2010-273858 has proposed a method of shortening the time taken to be ready for image sensing by changing the timeout time from the energization of a circuit for setting an image sensing enable state in accordance with the input state of patient information and an image sensing protocol.
In addition, in a conventional radiation imaging system, a radiation imaging apparatus performs image sensing upon matching the timing of radiation generation with the timing of image sensing by the radiation imaging apparatus by communication between a radiation generation apparatus and the radiation imaging apparatus. Recently, in order to simplify a system configuration required for communication, for example, according to Japanese Patent Laid-Open No. 2009-219538, there has been developed a radiation imaging system based on a scheme which performs image sensing immediately after the detection of radiation by the radiation imaging apparatus without performing communication between a radiation generation apparatus and the radiation imaging apparatus. In this radiation imaging system, ensuring a wide dynamic range covering a low dose of emitted radiation to a high dose of emitted radiation will cause a circuit for driving conversion elements and other electric circuit elements to generate noise such as thermal noise and shot noise. This reduces the S/N ratio in a low-dose region, in particular, resulting in a deterioration in the image quality of an obtained radiation image. Setting the sensor in an image sensing enable state for a predetermined time or more will increase the influence of noise. For this reason, the sensor is set in an image sensing disable state (sleep mode) by stopping driving the sensor to reset electric charges accumulated in the conversion elements. This reduces noise and suppresses a deterioration in image quality.
In the method disclosed in Japanese Patent Laid-Open No. 2010-273858, when it takes much time to input patient information and an image sensing protocol, the remaining time for actual image sensing decreases. For example, a timeout occurs during matching with the respiratory timing of a patient, and the sensor is set in the image sensing disable state. The sensor therefore needs a predetermined waiting time to enter the image sensing enable state again.
In addition, according to Japanese Patent Laid-Open No. 2009-219538, if the operator performs radiation irradiation without noticing that the apparatus has stopped driving the sensor and set it in the image sensing disable state, the apparatus may fail to perform desired radiation imaging (misshooting).
The present invention provides a radiation imaging technique which can perform radiation imaging while saving power and ensuring a sufficient image sensing time for actual image sensing.